The objectives of this study are to determine if transitioning conventional sedation to dexmedetomidine safely facilitates tracheal extubation after study initiation; alters the amounts of sedative and analgesic agents required after study initiation; influences the levels of sedation and analgesia; alters the adverse event profile (neurologic, hemodynamic, or gastrointestinal) during and after discontinuing sedation; and impacts the total cost of sedation during and after discontinuing sedation.